1. Field of the Invention
The present invention relates to encased assemblies comprising semiconductor devices, and more particularly to high power semiconductor rectifiers and thyristors.
2. Description of the Prior Art
Disc-type assembly of power semiconductor devices is generally known in the art. The purpose of such disc-type assembly is to encapsulate the basic semiconductor element. The basic semiconductor element typically consists of a silicon wafer soldered to a molybdenum base or a three piece molybdenum-silicon-molybdenum sandwich. The state of the art is to encapsulate the semiconductor element in a ceramic case which consists of at least two major members. One member of the case being a metal contact or pole piece brazed to a ceramic cylinder forming a cup-shaped housing in which the basic semiconductor element is placed. Another member of the case comprises a metal contact or pole piece to be applied to the other side of the semiconductor element. Both members of the case having outwardly extending weld flanges at the periphery. Encapsulation is achieved by mounting the semiconductor element on the pole piece within the ceramic housing, then covering the element with the other pole piece and welding the two flanges together.
Recent developments in the art have brought about cost reduced versions of the expensive ceramic to metal weld-type assemblies. Such an improvement is set forth in U.S. Pat. No. 3,443,168 relating to resin encapsulated, compression bonded, disc-type semiconductor device assemblies. The present invention discloses an improvement upon the invention of U.S. Pat. No. 3,443,168.